PROJECT SUMMARY/ABSTRACT Significant neurodevelopmental delay is emerging as one the most important current challenges for patients with congenital heart disease (CHD). Clinical studies demonstrate that reduced oxygen delivery due to CHD in utero results in subnormal brain development. Newly-developed brain injury after cardiac surgery is also common in neonates whose brains are already dysmature at the time of surgery. However no treatment options are currently available for brain damage in children with CHD. Our series of studies show that potential cell-based interventions for improvement of CHD-induced brain damage include: 1) promoting white matter (WM) regeneration through endogenous oligodendrocyte progenitors; 2) restoring the neurogenic potential of subventricular zone (SVZ) neural stem/progenitor cells; and 3) controlling prolonged microglia activation after cardiopulmonary bypass (CPB)-induced insults. Mesenchymal stromal cells (MSCs) are multipotent, nonhematopoietic cells that possess both immunomodulatory and regenerative properties, and can treat a wide range of diseases including hypoxic brain injury. Various rodent studies have shown that in the brain MSCs: 1) accelerate WM remyelination through the activation of endogenous oligodendrocyte progenitors; 2) promote neurogenesis from SVZ neural stem/progenitor cells; and 3) regulate microglia activation after hypoxic-ischemic brain insults. Multiple clinical trials have also established the safety of MSC-based therapy. These findings have led to our principal hypothesis that: MSC delivery to the early postnatal brain promotes endogenous regeneration of damaged neuronal and glia cells in children with CHD. Pediatric cardiac surgery provides a unique opportunity to control cerebral perfusion of the developing brain though CPB. We are proposing the use of CPB itself as a new MSC delivery system in the CHD population. The proposed project will test the following specific related hypotheses: 1) MSCs govern CPB-induced systemic inflammation and reduce microglia activation in the brain (Aim 1); 2) MSC delivery accelerates WM regeneration through activation of endogenous oligodendrocyte progenitors (Aim 2); 3) MSC treatment promotes cortical regeneration through activation of endogenous SVZ neural stem/progenitor cells (Aim 3). Using our unique porcine hypoxia and CPB model, we will determine: 1) the systemic effect of MSC delivery through CPB during CHD surgery (Aim 1); 2) the effect of MSC treatment on WM oligodendrocyte progenitors (Aim 2); and 3) the effect of MSC treatment on SVZ neural stem/progenitor cells (Aim 3). The goal of the project is to design novel cell-based therapies aimed at regenerating damaged neural and glial cells, and improving neurodevelopment in children with CHD. Since the cellular/anatomical structure and developmental process of the piglet brain closely resemble their human counterpart, the results will also assist in providing new regenerative approaches to a wide variety of perinatal hypoxic/ischemic brain damages.